I have a cousin named Gressa. She claims that its Greek, meaning 'grace'.
But I looked it up, and the more common spelling seems to be Gresa. And all I can find is that its Norwegian for 'grass'. Or its also a variant of an Albanian name. So I have yet to validate her story.
Also, I have no idea how those versions of the name are pronounced, but my cousin says it greh-sah.